I know many people hate algae because it is unsightly. But is it detrimental to the fish or the aquarium system? Is algae toxic? can it kill a fish? Or is it like any other plant? (photosynthesis, absorptioon of ammonia, etc...

I had some ugly brown diatoms forming on the glass and rocks so I woped that off. Right now I have a little bit of (a nice bright green color) hair algae on my driftwood that I left alone. It truth,I like the way it looks. Makes it look more natural. I noticed that its bubbling like crazy. It is constantly releasing tiny (absolutely tiny) bubbles. Are these oxygen bubbles? If it is, then thats good isnt it?

I dont plant on letting my tank get overgrown with algae. But if it's not dangerous, I wont mind having a little of it here and there.

The main objection to algae is it is unsightly. There are some other potential issues with it. Some types can clog your filter and cause decreased flow. If you have a planted tank, algae is bad because it steals nutrients from the water that the plants need. Depending on the type of algae, it can also be an indicator of poor water quality which is not good (although the algae itself isn't harmful in this case, just a sign). Lastly while algae does produce oxygen in the day time (which is probably what those bubbles are), during the night it consumes oxygen. While the consumption is relatively small compared to production, if you let your tank just totally be consumed by algae it could be a problem. If you like the looks of it, no reason you can't keep it, just keep an eye on it, for it will multiply quickly.